As is known, some integrated circuits have internal built-in self-test (BIST) capabilities. A built-in self-test is a function that can verify all or a portion of the internal functionality of an integrated circuit. Some types of integrated circuits have built-in self-test circuits built directly onto the integrated circuit die. Typically, the built-in self-test is activated by external means, for example, a signal communicated from outside the integrated circuit to dedicated pins or ports on the integrated circuit. For example, an integrated circuit that has a memory portion can include a built-in self-test circuit, which can be activated by a self-test signal communicated from outside the integrated circuit. The built-in self-test circuit can test the memory portion of the integrated circuit in response to the self-test signal.
Conventional built-in self-test circuits do not allow the integrated circuit to perform its intended function while the built-in self-test is being performed. Instead, during the built-in self-test, the built-in self-test circuit exercises all of, or parts of, circuits on the integrated circuit in particular ways that do not necessarily allow concurrent operation of functions that the integrated circuit is intended to perform. Therefore, the built-in self-test is typically only activated one time, for example, upon power up of the integrated circuit, or from time to time. At other times, the built-in self-test circuit and function are dormant and the integrated circuit can perform its intended function.